(1) Field of the Invention
The present invention relates to a display device for use in an electronic appliance such as a FA appliance, AV appliance, OA terminal etc., as well as an advertisement display.
(2) Description of the Prior Art
The prior art will be described with reference to FIGS. 1 through 4. FIG. 1 Is a perspective view showing a conventional display device; FIG. 1A is a view from the obverse side of the display device and FIG. 1B is a view from the reverse side thereof. FIG. 2 contains diagrams showing the forces and their components when the input connector is inserted. FIG. 3 is a sectional view showing a prior art display device. FIG. 4 is a sectional view showing another prior art display device.
As shown in FIG. 1, the conventional display device comprises: a display panel 2; a scan signal input circuit substrate 13 disposed along the length of one side of display panel 2 for inputting the scan signal to display panel 2; and a data signal input circuit substrate 14 disposed along the length of the other side for inputting data to the display panel 2. The display panel 2 is composed of a pair of glass substrates for inputting the scan signal and data, respectively, and a liquid crystal material sealed therein; each glass substrate has a pattern of electrode leads (designated at 3 in FIG. 2), which consists of tin oxide, indium oxide or the like, formed on the opposing surface to the other. This pattern of electrode leads 3 is joined to a flexible circuit substrate 8 so that the display panel 2 is electrically connected to scan signal input circuit substrate 13 having, for example, an input connector 5, electronic parts 9, driver ICs 18 etc. provided thereon.
FIG. 2A is a sectional view cut along a plane 300--300 in FIG. 1A, showing the detailed configuration of the above electric connection. In the figure, a glass terminal 4 of display panel 2 and scan signal input circuit substrate 13 are placed opposedly with a gap 16 therebetween so that pattern of electrode leads 3 formed on glass terminal 4 is connected with scan signal input circuit substrate 13 by flexible circuit substrate 8. The joint between pattern of electrode leads 3 and flexible circuit substrate 8 is protected by resin 6.
In this conventional arrangement the thus configured joint in some cases peeled off due to the stress generated in pattern of electrode leads 3 and/or flexible circuit substrate 8 extending across gap 16 when input connector 5 was handled f or attachment or removal. For example, suppose that a force f.sub.0 is applied when input connector 5 is handled for attachment or removal as shown in FIG. 2A. In this case, force f.sub.0 can be decomposed into force component f.sub.1 acting on spacer 15 and force component f.sub.2 acting at the joint of flexible circuit substrate 8. This force component f.sub.2 would cause the peeling.
Next, this peeling force will be explained with reference to FIG. 2B.
Force f.sub.0 applied on input connector 5 can be decomposed into force component f.sub.1 shown in expression (1) and force component f.sub.2 shown in expression (2) as follows: EQU f.sub.1 =(X/Y).multidot.f.sub.0 (1) EQU f.sub.2 =[1-(X/Y)].multidot.f.sub.0 (2)
where f.sub.0 : connector insertion force;
f.sub.1 : spacer pressing force; PA1 f.sub.2 : stress; PA1 X: distance between f.sub.0 and f.sub.2 ; and PA1 Y: distance between f.sub.1 and f.sub.2. PA1 a display panel; PA1 a circuit substrate disposed, at the periphery of and beside, the display panel with a predetermined gap therebetween; PA1 a flexible circuit substrate extending across the gap to connect the display panel with the circuit substrate; and PA1 a reinforcing plate having a plurality of connecting parts to be joined to the circuit substrate and a fixture portion to be fixed to the display panel, and is characterized in that the reinforcing plate is fixed to the circuit substrate and display panel, on the side opposite to the one on which the flexible circuit substrate is provided. PA1 a display panel; PA1 a circuit substrate disposed, at the periphery of and beside, the display panel with a predetermined gap therebetween; PA1 a flexible circuit substrate extending across the gap to connect the display panel with the circuit substrate; and PA1 a reinforcing plate having a fixture portion to be fixed to the display panel and a plurality of connecting parts each of which is bent and stepped so as to be joined to the circuit substrate, on the side where the flexible circuit substrate is provided, and is characterized in that the fixture portion of the reinforcing plate is fixed to the side of the display panel, opposite to the one on which the flexible circuit substrate is provided, while the connecting parts are extended passing through the gap to the side on which the flexible circuit substrate is provided, and joined to the circuit substrate on the side thereof.
This force component f.sub.2 warps flexible circuit substrate 8. If this bending is represented by an angle .theta., the component of force along flexible circuit substrate 8 which is deformed results in f.sub.2 sin .theta.. Further, as shown in FIG. 2C, this force causes a peeling force F of f.sub.2 sin.sup.2 .theta., thus separating flexible circuit substrate 8 from anisotropic conductive film 7 having pattern of electrode leads 3 formed on glass terminal 4. Force component f.sub.1 of force f.sub.0 is borne by a bezel 12. Here, FIG. 2C is an enlarged view of an encircled portion D in FIG. 2A.
Various countermeasures have conventionally been taken against the above problem.
The first method is one in which, as shown in FIG. 2A, resin 6 of an epoxy or acrylic type is filled in the joint with glass terminal 4 so as to integrate display panel 2 with flexible circuit substrate 8.
The second method is that disclosed in Japanese Patent Application Laid-Open Hei 4 No. 269,723, as shown in FIG. 3 in which the gap between glass terminal 4 and scan signal input circuit substrate 13 is provided with resin 6 so as to fill up the space which might, otherwise, cause the deformation.
Further, the third method is disclosed in Japanese Patent Application Laid-Open Hei 8 No. 152,644, as shown in FIG. 4. That is, glass terminal 4 and scan signal input circuit substrate 13 are made to abut each other at their end faces while a reinforcing plate 19 is disposed across the non-displaying area of display panel 2 and the entire surface of scan signal input circuit substrate 13 and bonded with resin 6.
However, the first method cannot provide high enough strength to stop peeling, as already stated.
In the second method, the rigidity of the structure is enhanced since the gap between glass terminal 4 and scan signal input circuit substrate 13 is filled up with resin 6. This method, however, needs a prolonged time for application and drying of resin 6 and handling will become difficult when scan signal input circuit substrate 13 needs to be detached for repair.
In the third method, the strength to stop peeling can be enhanced, but the handling will be degraded as in the second embodiment. Further, since reinforcing plate 19 is applied throughout the rear surface of scan signal input circuit substrate 13, all electric parts such as driver ICs 18 etc., must be mounted on the obverse face of scan signal input circuit substrate 13. This configuration constrains the arrangement of the parts and increases cost due to the use of reinforcing plate 19.